U.S. patent application number 10/106065 was filed with the patent office on 2002-10-03 for lens driving apparatus and lens barrel.
This patent application is currently assigned to FUJI PHOTO OPTICAL CO, LTD.. Invention is credited to Onda, Kazuhiko.
Application Number | 20020141081 10/106065 |
Document ID | / |
Family ID | 18950178 |
Filed Date | 2002-10-03 |
United States Patent
Application |
20020141081 |
Kind Code |
A1 |
Onda, Kazuhiko |
October 3, 2002 |
Lens driving apparatus and lens barrel
Abstract
A lens driving apparatus 1 in accordance with the present
invention comprises a lead screw 11 rotated by a driving source 2;
a nut plate 4 formed with a female threaded part 14 in mesh with a
threaded part 12 of the lead screw 11 and adapted to move along the
optical axis O as the lead screw 11 rotates; a lens holding frame
3, provided so as to abut against the nut plate 4 while being
slidable with respect to a guide shaft 25 extending along the
optical axis O, for holding a lens 10; and urging means 5 for
urging the lens holding frame 3 against the nut plate 4. In this
lens driving apparatus 1, the lens holding frame 3 moves along the
optical axis O as the nut plate 4 provided separately from the lens
holding frame 3 moves.
Inventors: |
Onda, Kazuhiko;
(Saitama-shi, JP) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
700 THIRTEENTH ST. NW
SUITE 300
WASHINGTON
DC
20005-3960
US
|
Assignee: |
FUJI PHOTO OPTICAL CO, LTD.
Saitama-shi
JP
|
Family ID: |
18950178 |
Appl. No.: |
10/106065 |
Filed: |
March 27, 2002 |
Current U.S.
Class: |
359/823 ;
359/819; 359/822 |
Current CPC
Class: |
G02B 7/102 20130101 |
Class at
Publication: |
359/823 ;
359/819; 359/822 |
International
Class: |
G02B 007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2001 |
JP |
2001-096244 |
Claims
What is claimed is:
1 A lens driving apparatus for moving a lens along an optical axis,
said lens driving apparatus comprising: a lead screw rotated by a
driving source; a nut plate formed with a threaded part in mesh
with a threaded part of said lead screw and adapted to move along
said optical axis as said lead screw rotates; a lens holding frame
for holding said lens, provided so as to abut against said nut
plate while being slidable with respect to a guide shaft extending
along said optical axis; and urging means for urging said lens
holding frame against said nut plate.
2 A lens driving apparatus according to claim 1, wherein said
threaded part of said nut plate is less than one pitch.
3 A lens driving apparatus according to claim 1, wherein said lens
holding frame abuts against said nut plate about said lead
screw.
4 A lens driving apparatus according to claim 1, wherein said nut
plate has a through hole through which said guide shaft
penetrates.
5 A lens driving apparatus according to claim 4, wherein said
through hole is a slot.
6 A lens driving apparatus according to claim 1, wherein said lens
is a focus lens for adjusting focus in a taking optical system.
7 A lens barrel comprising: moving means for moving the lens
driving apparatus according to claim 1 to an accommodating position
along said optical axis; and separating means for separating said
lens holding frame from said nut plate at a predetermined position
by abutting against said lens holding frame when said lens driving
apparatus is moved by said moving means to said accommodating
position.
8 A lens barrel according to claim 7, wherein said separating means
is a boss, disposed at said accommodating position, projecting by a
predetermined amount along said optical axis.
9 A lens barrel according to claim 7, wherein said separating means
is a boss, disposed in said lens holding frame, projecting by a
predetermined amount along said optical axis.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a lens driving apparatus
for moving a lens, specifically a focus lens for adjusting focus,
along an optical axis; and a lens barrel comprising such lens
driving apparatus.
[0003] 2. Related Background Art
[0004] Japanese Patent Application Laid-Open No. 2000-275494
discloses a lens driving mechanism for moving a lens along its
optical axis. This lens driving mechanism comprises a motor having
a lead screw extending along the optical axis as a rotary driving
shaft; a bridge having a thread hole in mesh with a threaded part
of the lead screw; and a lens holding frame, connected to the
bridge, for holding the lens. As the lead screw rotates, the bridge
moves along the optical axis, whereby the lens holding frame can be
moved along the optical axis. The lens holding frame is slidably
attached to a guide shaft extending along the optical axis, whereby
the lens holding frame is guided so as to move along the optical
axis.
[0005] Also, Japanese Patent Application Laid-Open No. Hei7-43583
discloses a lens driving apparatus for moving a lens along its
optical axis. This lens driving apparatus comprises a motor having
a lead screw extending along the optical axis as a rotary driving
shaft; a nut in mesh with a threaded part of the lead screw; and a
lens holding frame, formed with an accommodating part for
accommodating the nut, for holding the lens. As the lead screw
rotates, the nut moves along the optical axis, whereby the lens
holding frame moves with the nut along the optical axis.
[0006] Further, Japanese Patent Application Laid-Open No.
2000-194045 discloses a lens barrel having a plurality of lens
cylinders and enabling them to expand/collapse in a multistage
fashion between an accommodating position and a use starting
position. Disposed within the lens barrel is a lens driving
apparatus for moving the lens along its optical axis.
SUMMARY OF THE INVENTION
[0007] In such a conventional lens driving mechanism, however, the
bridge or nut in mesh with the lead screw and the lens holding
frame slidably attached to the guide shaft are connected to each
other or accommodated together, thereby substantially being
integrated with each other. Therefore, when the axis of the lead
screw shifts from the axis of the guide shaft, snagging may occur,
thereby generating such inconveniences as malfunctioning,
deformation in each member, and shifting of the optical axis.
Further, it is problematic in that "rattling" is likely to occur
due to the backlash in meshing parts.
[0008] Also, in the conventional lens barrels mentioned above,
electric control is carried out such that the lens of the lens
driving apparatus do not come into contact with other members when
the lens cylinders are collapsed to its accommodating positions.
Therefore, they are problematic in that the apparatus configuration
is complicated, and are inconvenient in that an operation for
accommodating them takes time.
[0009] Hence, it is an object of the present invention to provide a
lens driving apparatus which suppresses the occurrence of
inconveniences such as malfunctioning, deformation of members, and
shifting of the optical axis.
[0010] It is another object of the present invention to provide a
lens barrel in which accommodating operation can be carried out
without electric control while preventing the lens from coming into
contact with other members.
[0011] For achieving the above-mentioned object, the lens driving
apparatus in accordance with the present invention is a lens
driving apparatus for moving a lens along an optical axis, the lens
driving apparatus comprising a lead screw rotated by a driving
source; a nut plate formed with a threaded part in mesh with a
threaded part of the lead screw and adapted to move along the
optical axis as the lead screw rotates; a lens holding frame for
holding the lens, provided so as to abut against the nut plate
while being slidable with respect to a guide shaft extending along
the optical axis; and urging means for urging the lens holding
frame against the nut plate.
[0012] According to such a lens driving apparatus, the lens holding
frame abuts against the nut plate while being urged against the nut
plate by the urging means, thereby moving along the optical axis as
the nut plate moves.
[0013] Since the urging action caused by the urging means is
transmitted to the nut plate byway of the lens holding frame, the
nut plate moves by the amount of backlash with respect to the lead
screw, thereby being biased.
[0014] Preferably, the threaded part of the nut is less than one
pitch. As a consequence, even when an error exists in each pitch
width of the lead screw, friction/load is restrained from occurring
as the lead screw rotates.
[0015] Also, forming the threaded part into less than one pitch
simplifies the die-cutting step when molding the nut plate.
[0016] Further, it contributes to making the whole apparatus
smaller.
[0017] Preferably, the lens holding frame abuts against the nut
plate about the lead screw. When the nut plate meshes with the lead
screw, "rattling" occurs due to the backlash therebetween. When the
lens holding frame and the nut plate are thus designed so as to
abut against each other about the lead screw such that the movement
of the nut plate is transmitted to the lens holding frame by way of
the abutting part, the influence of "rattling" can be reduced.
[0018] Preferably, the nut plate has a through hole through which
the guide shaft penetrates. This can prevent the nut plate from
rotating together with the lead screw as the lead screw
rotates.
[0019] Preferably, the through hole is a slot. Such structure
absorbs the deviation between the axis of the lead screw and the
axis of the guide shaft, thereby preventing malfunctions from
occurring due to axial misalignment.
[0020] The lens may be a focus lens for adjusting focus in a taking
optical system.
[0021] The lens barrel in accordance with the present invention
comprises moving means for moving the above-mentioned lens driving
apparatus to an accommodating position along the optical axis; and
separating means for separating the lens holding frame from the nut
plate at a predetermined position by abutting against the lens
holding frame when the lens driving apparatus is moved by the
moving means to the accommodating position.
[0022] In such a lens barrel, in an accommodating operation of the
lens driving apparatus, the separating means separates the lens
holding frame from the nut plate by abutting against the lens
holding frame, so that the lens can be stopped at a predetermined
position, whereby collisions with other members can be prevented
from occurring.
[0023] Examples of separating means include a boss, disposed at the
accommodating position of the lens barrel, projecting by a
predetermined amount along the optical axis; and a boss, disposed
in the lens holding frame, projecting by a predetermined amount
along the optical axis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a sectional view of the lens driving apparatus in
accordance with an embodiment;
[0025] FIG. 2 is a front view of the lens driving apparatus seen in
the direction B in FIG. 1;
[0026] FIG. 3 is a sectional view of a lens barrel in which the
lens driving apparatus in accordance with the embodiment is
incorporated;
[0027] FIG. 4 is a sectional view of the lens barrel in which the
lens driving apparatus in accordance with the embodiment is
incorporated; and
[0028] FIG. 5 is a sectional view of a modified example of the lens
barrel shown in FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] In the following, the lens driving apparatus in accordance
with embodiments of the present invention will be explained with
reference to the drawings. In the following explanation, parts
identical or equivalent to each other will be referred to with
numerals or letters identical to each other without repeating their
overlapping descriptions.
[0030] FIG. 1 is a sectional view of the lens driving apparatus in
accordance with an embodiment. FIG. 2 is a front view of the lens
driving apparatus seen in the direction B in FIG. 1 (wider than the
range of B shown in FIG. 1). This lens driving apparatus 1 is one
for moving a focus lens 10, which adjusts focus in a taking optical
system, along the optical axis O. The lens driving apparatus 1
comprises a focus motor 2 as a driving source, a nut plate 4 which
moves along the optical axis O as being driven by the focus motor
2, and a lens holding frame 3 for holding the focus lens 10 and
moving along the optical axis O as the nut plate 4 moves.
[0031] The focus motor 2 is fastened to a second lens group frame
75 (explained later) with a screw 22 byway of a holding plate 21.
This yields a structure by which the position of focus motor 2 is
hard to move when it is driven.
[0032] The focus motor 2 has a lead screw 11 which extends along
the optical axis O. The nut plate 4 has a female threaded part 14
in mesh with a threaded part 12 of the lead screw 11 with a
predetermined amount of backlash. Since the nut plate 4 is in mesh
with the lead screw 11 while having a predetermined amount of
backlash, fluctuations of the nut plate 4 and lead screw 11 as
products are absorbed, whereby inconveniences such as snagging
generated in the meshed state making them unmovable are prevented
from occurring. Here, the female threaded part 14 is not always
required to have an annular form, but can be formed like letter U,
for example, as long as it can mesh with the lead screw 11.
[0033] The female threaded part 14 of the nut plate 4 is set to
less than one pitch. This reduces the part in mesh with the
threaded part 12 of the lead screw 11, which makes it easier to
absorb fluctuations among products, whereby friction/load is hard
to occur due to an error in each pitch width of the threaded part
12 of the lead screw 11 if any. Further, configuring it into less
than one pitch makes it unnecessary to pull dies while rotating
them in the die-cutting step at the time of molding the nut plate
4, thereby being advantageous in that the manufacturing step is
simplified and in that the lens driving apparatus 1 can reduce its
size.
[0034] The lens holding frame 3 abuts against the nut plate 4 about
the lead screw 11. The lens holding frame 3 is urged by a
compression spring 5, acting as urging means, against the nut plate
4 along the optical axis O. As a consequence, the lens holding
frame 3 keeps its state abutting against the nut plate 4, whereby
the lens holding frame 3 moves along the optical axis O together
with the nut plate 4 when the latter moves along the optical axis O
(while a guide shaft 25 is disposed between the second lens group
frame 75 and a stopper plate 76). The lens holding frame 3 moves
along the optical axis O more accurately, since it is placed
slidable with respect to the guide shaft 25 extending along the
optical axis O. The guide shaft 25 is biased along the optical axis
O by a fastening spring 27, so as to be prevented from moving by
itself along the optical axis O.
[0035] As can also be seen from the drawing, the lens holding frame
3 and the nut plate 4 are provided separately from each other. The
lens holding frame 3 moves along the optical axis O being guided by
the guide shaft 25, while being pressed against the nut plate 4 and
thereby receiving moving action of the nut plate 4, instead of the
lens holding frame 3 and nut plate 4 being integrally attached to
each other or the lens holding frame 3 meshing with the lead screw
11 and directly receiving the rotary driving force of the lead
screw 11. Therefore, even when the axis of the lead screw 11 shifts
from the optical axis O, inconveniences such as malfunctioning,
deformation of each member, and deterioration of optical
performances can be prevented from occurring.
[0036] When the nut plate 4 meshes with the lead screw 11,
"rattling" occurs due to the backlash therebetween. In this
embodiment, the urging action caused by the compression spring 5
presses the nut plate 4 by way of the lens holding frame 3, whereby
the nut plate 4 moves by the amount of backlash with respect to the
lead screw 11, so as to be biased. This suppresses the occurrence
of "rattling" in the nut plate 4, thereby improving the positioning
accuracy of the lens holding frame 3. Also, the lens holding frame
3 is less susceptible to influences of "rattling" and "tilts" of
the nut plate 4 resulting from the backlash, since it is designed
so as to abut against the nut plate 4 about the lead screw 11.
[0037] The nut plate 4 is formed with a through hole 4a through
which the guide shaft 25 penetrates. This prevents the nut plate 4
from rotating together with the lead screw 11 as the latter
rotates. Here, the through hole 4a is formed like a slot. This
absorbs the deviation between the axis of lead screw 11 and the
axis of guide shaft 25, whereby malfunctions and the like are
prevented from occurring due to axial misalignment.
[0038] FIGS. 3 and 4 are sectional view of a lens barrel in which
the lens driving apparatus in accordance with this embodiment is
incorporated. FIG. 3 shows a state where an intermediate cylinder
83 and a movable cylinder 84 are expanded. FIG. 4 shows a state
where the intermediate cylinder 83 and the movable cylinder 84 are
collapsed. The lens barrel 80 in accordance with this embodiment is
used in a taking optical system of a digital camera. The lens
barrel 80 comprises a rotary cylinder 81, a fixed frame 82 to which
a CCD (Charged Coupled Device) 85 for carrying out photoelectric
conversion is attached by way of a CCD holding frame 89, the
intermediate cylinder 83 in which a second lens group 87 and the
lens driving apparatus 1 are placed by way of the second lens group
frame 75, and the movable frame 84 in which the first lens group 86
is placed. The first lens group 86, the second lens group 87, and
the focus lens 10 constitute the taking optical system of the
digital camera.
[0039] Optical information of an image captured through the lens
groups 86, 87 is received by a light-receiving surface 88 and is
converted by the CCD 85 into an electric signal, whereby an
electric signal pattern is formed. The image formed by this
electric signal pattern can be seen through a liquid crystal
monitor or the like placed in a digital camera body 90. The focus
lens 10 adjusts focus in the taking optical system. The lens barrel
80 in accordance with this embodiment expands and collapses the
intermediate cylinder 83 and movable cylinder 84, thereby realizing
a zooming function in such a digital camera. Configurations for
carrying out these expanding and collapsing operations will now be
explained.
[0040] The peripheral face of the fixed frame 82 is formed with a
cam groove 95. The cam groove 95 penetrates through the peripheral
face of the fixed frame 82, and is formed into a spiral along the
peripheral face. A cam follower 92 of the intermediate cylinder 83
is inserted in the cam groove 95. The cam follower 92 is a
protrusion, formed in the outer peripheral face of the intermediate
cylinder 83, projecting from the outer peripheral face to the
outside. A pin 93 is attached to the leading end part of the cam
follower 92. The pin 93 is inserted in a longitudinal groove 94
formed in the inner peripheral face of the rotary cylinder 81, and
transmits the turning force of the rotary cylinder 81 to the
intermediate cylinder 83 as the rotary cylinder 81 rotates. The
rotary cylinder 81 is a tubular member disposed on the outside of
the fixed frame 82, and rotates in response to the driving force of
an expanding/collapsing motor (not depicted) which is placed in the
digital camera body 90. The longitudinal groove 94 is formed by
denting the inner peripheral face of the rotary cylinder 81 and
extends along the optical axis O of the taking optical system.
[0041] As the rotary cylinder 81 rotates, the pin 93 and cam
follower 92 move not only circumferentially along the cam groove 95
spirally formed in the fixed frame 82, but also along the optical
axis O while being guided by the longitudinal groove 94.
Consequently, the intermediate cylinder 83 moves along the optical
axis O while rotating, thereby expanding or collapsing with respect
to the fixed frame 82.
[0042] A linearly-advancing key ring 97, which is an annular member
having a diameter substantially the same as that of the
intermediate cylinder 83, engages the rear end part of the
intermediate cylinder 83 so as to be rotatable relative to the
intermediate cylinder 83. The inner peripheral face of the fixed
frame 82 is formed with a longitudinal groove 96 extending along
the optical axis O, whereas the linearly-advancing key ring 97 also
fits in the longitudinal groove 96. This fitting prevents the
linearly-advancing key ring 97 from rotating. As a consequence, the
linearly-advancing key ring 97 moves along the optical axis O
together with the intermediate cylinder 83 while in a state not
rotating together with the intermediate cylinder 83.
[0043] The linearly-advancing key ring 97 is formed with a support
part 97a extending forward along the optical axis. The support part
97a engages the rear end part of the movable cylinder 84, thereby
preventing the movable cylinder 84 from rotating. The rear end of
the movable cylinder 84 is provided with a pin 98 projecting from
the outer peripheral face. The pin 98 is inserted in a cam groove
99 formed in the inner peripheral face of the intermediate cylinder
83. The cam groove 99 is formed spirally along the inner peripheral
face of the intermediate cylinder 83.
[0044] Since the movable cylinder 84 is supported by the support
part 97a of the linearly-advancing key ring 97, it does not rotate
together with the intermediate cylinder 83 when the latter rotates.
As a consequence, the pin 98 rotates relatively with respect to the
intermediate cylinder 83 and moves in conformity to the spiral form
of the cam groove 99. Therefore, as the intermediate cylinder 83
rotates, the movable cylinder 84 moves along the optical axis O,
thereby expanding or collapsing with respect to the intermediate
cylinder 83.
[0045] In this embodiment, the expanding/collapsing motor and the
constituents (cam grooves 95, 99, cam follower 92, pins 93, 98,
linearly-advancing key ring 97, etc.) enabling the intermediate
cylinder 83 and movable cylinder 84 to expand/collapse in response
to the rotation of the expanding/collapsing motor function as
moving means. Driving the moving means makes it possible to adjust
distances between the lens groups 86, 87 and light-receiving
surface 88, thereby realizing a zooming function (while the second
lens group 87 and focus lens 10 are movable along the optical axis
O relative to the intermediate cylinder 83).
[0046] When moving the lens driving apparatus 1 placed in the
intermediate cylinder 83 to its accommodating position, the
intermediate cylinder 83 and movable cylinder 84 are moved by the
moving means along the optical axis O, so as to be collapsed into
the fixed frame 82. Here, a separating means 90 for separating the
lens holding frame 3 and the nut plate 4 from each other is
disposed at a position where the lens holding frame 3 of the lens
driving apparatus 1 is accommodated. In this embodiment, the
separating means is a boss 90, formed on the CCD holding frame 89,
projecting by a predetermined amount along the optical axis O. When
the intermediate cylinder 83 and movable cylinder 84 are collapsed
into the fixed frame 82, the boss 90 stops the lens holding frame 3
from moving at a predetermined position by abutting against a boss
receiving part 91 of the lens holding frame 3, thereby separating
it from the nut plate 4 (see FIG. 4). As a consequence, the lens 10
can be stopped at a safe position where it neither collides nor
comes into contact with other members. Since the boss 90 separates
the lens holding frame 3 from the nut plate 4 by abutting against
the boss receiving part 91 of the lens holding frame 3, it can stop
the lens 10 rapidly and correctly at a safe position without
electric control. Such an effect is realized due to the fact that
the lens holding frame 3 and the nut plate 4 are provided
separately from each other. Alternatively, as shown in FIG. 5, the
lens holding frame 3 may be provided with the boss 90, as the
separating means, which is configured so as to abut against the
boss receiving part 91 formed on the CCD holding frame 89.
[0047] Though the present invention is specifically explained
according to its embodiments in the foregoing, the present
invention is not limited to the above-mentioned embodiments when
being carried out, but includes all the modifications of the
invention falling within the scope of claims of the present
invention, and can be modified in terms of its form, size,
arrangement, configuration, and the like.
[0048] For example, though an example in which the lens driving
apparatus 1 is applied to a digital camera body is shown, it is
also applicable to lens optical systems of cameras for taking
photographs by using silver halide films and other optical
devices.
* * * * *